Bismaleimides per se occupy a prominent position in the spectrum of thermoset resins. Indeed, several bismaleimides are commercially available. The co-cure of simple bismaleimides with relatively simple divinyl ethers is also known in the art. However, neither simple bismaleimides nor bismaleimide/divinyl ether systems are believed to have received application in the area of die attach adhesives. In this context, several criteria are believed to be critical to successful commercial application:
1. The adhesive composition should have good handling properties, without the need to add solvent thereto (i . e., a 100% reactive liquid monomer system of sufficiently low viscosity); PA1 2. The adhesive composition should be capable of rapid ("snap") cure, i.e., two minutes or less at .ltoreq.200.degree. C.; PA1 3. The resulting thermoset should be stable to at least 250.degree. C., wherein "stable" is defined as less than 1% weight loss at 250.degree. C. when subjected to a temperature ramp of 10.degree. C./min. in air via thermogravimetric analysis (TGA) ; PA1 4. The resulting thermoset should be sufficiently flexible (radius of curvature &gt;1.0 meter) to allow use in a variety of high stress applications; PA1 5. The resulting thermoset should exhibit low-moisture uptake (to be used in nonhermetic packages); and PA1 6. The resulting thermoset should exhibit good adhesion to substrate, even after strenuous exposure to moisture. PA1 (a) a bismaleimide of defined structure, PA1 (b) up to one equivalent of a divinyl compound of defined structure per equivalent of bismaleimide, PA1 (c) in the range of 0.1 up to 10 wt % of at least one coupling agent, based on the total weight of the composition, and PA1 (d) in the range of 0.2 up to 3 wt % of at least one free radical initiator, based on the total weight of organic materials in the composition, i.e., in the absence of filler. PA1 --X-- is selected from: PA1 each R is independently as defined above, PA1 each Q is independently selected from --O--, --O--C(O)--, --C(O)-- or --C(O)--O--, and PA1 --Y-- is selected from: PA1 in the range of about 10 up to 80 wt % of the above-described adhesive composition, and in the range of about 20 up to 90 wt % filler. PA1 (a) applying the above-described adhesive composition to said first article, PA1 (b) bringing said first and second article into intimate contact to form an assembly wherein said first article and said second article are separated only by the adhesive composition applied in step (a), and thereafter, PA1 (c) subjecting said assembly to conditions suitable to cure said adhesive composition. PA1 (a) applying the above-described die attach paste to said substrate and/or said microelectronic device, PA1 (b) bringing said substrate and said device into intimate contact to form an assembly wherein said substrate and said device are separated only by the die attach composition applied in step (a), and thereafter, PA1 (c) subjecting said assembly to conditions suitable to cure said die attach composition. PA1 adding diamine to a solution of maleic anhydride, PA1 adding acetic anhydride to said solution once diamine addition is complete, and then allowing the resulting mixture to stir overnight, and thereafter PA1 treating the resulting reaction mixture with a suitable isomerizing agent.
With respect to the requirement for low moisture uptake by the thermoset, for example, relatively high moisture uptake is a known drawback of prior art bismaleimide thermosets. In addition, prior art systems have not provided the combination of properties desired for the applications contemplated herein.